This invention relates to a prism optical system for a color television camera and more particularly to improvements on a prism system provided with dichroic layers or colorselective reflecting layers capable of splitting a light into different color light components.
Generally, a color televison camera is provided with an optical system capable of splitting a light reflected from an objective into three primary color light components. The known types of such optical system include that which uses dichroic mirrors or color-separating mirrors and that which is provided with a prism system provided with dichroic layers. Particularly, the prism system using dichroic layers admits of a compact optical construction and is adapted for a handy color television camera.
The U.S. Pat. No. 3,202,039 allowed to Hendrik de Lang et al may be cited as an example of a prism system provided with dichroic layers for a color television camera. This United States patent discloses a prism system in which light beams reflected by the respective dichroic layers are again totally reflected by a flat air-glass transition surface. In the above-mentioned case where light beams reflected by the dichroic layers are again subjected to total reflection, the shape and position of the constituent prisms of the prism system should be determined with care taken to suppress the occurrence of polarization. This requirement tends to render the construction of the prism system considerably complicated. With the aforesaid United States patent, the direction in which three pickup tubes are arranged around the prism system is subject to considerable limitation due to the smaller structural freedom of the prism system. The resultant expanded radial arrangement of the pickup tubes relative to the prism system requires an unnecessarily large space in the color television camera, presenting difficulties in rendering said camera desirably compact.